Methods of producing isomerization catalysts

ABSTRACT

Methods of producing an isomerization catalyst include preparing a catalyst precursor solution, hydrothermally treating the catalyst precursor solution to produce a magnesium oxide precipitant, and calcining the magnesium oxide precipitant to produce the isomerization catalyst. The catalyst precursor solution includes at least a magnesium precursor, a hydrolyzing agent, and cetrimonium bromide. Methods of producing 1-butene from a 2-butene-containing feedstock with the isomerization catalyst are also disclosed.

BACKGROUND Field

The present disclosure generally relates to catalyst compositions and,more specifically, to isomerization catalysts, methods of making theisomerization catalysts, and methods of using the isomerizationcatalyst.

Technical Background

In recent years, there has been a dramatic increase in the demand for1-butene due to applications in the production of polyethylenes, such ashigh density polyethylene (HDPE) and low density polyethylene (LDPE),and polybutenes. Currently, a majority of the 1-butene producedworldwide is produced by the dimerization of high-value feedstocks, suchas ethylene, the dehydrogenation of butane, or separation from low-valueC₄ feedstocks. These low-value C₄ feedstocks may be by-products oreffluent streams from steam cracking units, which primarily produceethylene, Fluid Catalytic Cracking (FCC) units, which primarily producegasoline, or methyl tertiary butyl ether (MTBE) extraction units.However, these processes cannot respond adequately to the rapid increasein 1-butene demand. As a result, alternative methods to directly produce1-butene have been developed and, in particular, methods of producing1-butene from 2-butene-containing feedstocks.

The production of 1-butene from 2-butene-containing feedstocks can beaccomplished through the isomerization of the 2-butene to 1-butene.Isomerization of 2-butene to produce 1-butene can better meet thegrowing demand for 1-butene. Isomerization can be accomplished bycontacting 2-butene in the 2-butene-containing feedstock with anisomerization catalyst. However, conventional isomerization catalystsand, as a result, conventional 1-butene production processes areinefficient, often failing to convert a significant portion of 2-butenesand only resulting in a comparatively small 1-butene yield.

SUMMARY

Accordingly, there is an ongoing need for improved isomerizationcatalysts with increase catalytic activity that, as a result, increasethe conversion rate of 2-butene and the yield of 1-butene from a2-butene isomerization processes. The present disclosure is directed tomethods of producing an isomerization catalyst through the hydrothermalsynthesis of magnesium oxide. The present disclosure is also directed tomethods of producing 1-butene from a 2-butene-containing feedstockthrough isomerization with the isomerization catalyst of the presentdisclosure. The isomerization catalyst produced by the methods of thepresent disclosure may have increased thermal stability, which mayresult in a reduced deactivation rate of the isomerization catalyst whenutilized at temperatures sufficient to produce 1-butene from theisomerization of 2-butenes. Accordingly, the methods of the producing1-butene of the present disclosure may have increased efficiency, anincreased conversion rate of 2-butene and greater selectivity to andyield of 1-butene.

According to one or more embodiments of the present disclosure, a methodof producing an isomerization catalyst may comprise preparing a catalystprecursor solution comprising at least a magnesium precursor, ahydrolyzing agent, and cetrimonium bromide. Additionally, the method mayfurther comprise hydrothermally treating the catalyst precursor solutionto produce a magnesium oxide precipitant. The method may furthercomprise calcining the magnesium oxide precipitant to produce theisomerization catalyst.

According to one or more other embodiments of the present disclosure, amethod of producing 1-butene from a 2-butene-containing feedstock maycomprise contacting the 2-butene-containing feedstock with anisomerization catalyst to produce an isomerization reaction effluentcomprising 1-butene. The isomerization catalyst may be prepared by amethod comprising preparing a catalyst precursor solution comprising atleast a magnesium precursor, a hydrolyzing agent, and cetrimoniumbromide, treating the catalyst precursor solution to produce a magnesiumoxide precipitant, and calcining the magnesium oxide precipitant toproduce the isomerization catalyst.

Additional features and advantages of the technology described in thepresent disclosure will be set forth in the detailed description thatfollows and, in part, will be readily apparent to those skilled in theart from the description or recognized by practicing the technology asdescribed in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific embodiments of thepresent disclosure can be best understood when read in conjunction withthe following drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 schematically depicts a fixed bed continuous flow reactorincluding an isomerization reaction zone, according to one or moreembodiments of the present disclosure;

FIG. 2 schematically depicts another fixed bed continuous flow reactorincluding an isomerization reaction zone, according to one or moreembodiments of the present disclosure;

FIG. 3 graphically depicts the X-ray diffraction (XRD) profiles ofisomerization catalysts, according to one or more embodiments of thepresent disclosure;

FIG. 4 graphically depicts the 1-butene yield (y-axis) as a function oftime-on-stream (x-axis) obtained from a reactor for isomerizing a2-butene-containing feedstock, according to one or more embodiments ofthe present disclosure; and

FIG. 5 graphically depicts the 1-butene yield (y-axis) as a function oftime-on-stream (x-axis) obtained from a reactor for isomerizing abutene-containing feedstock, according to one or more embodiments of thepresent disclosure.

For the purpose of describing the simplified schematic illustrations anddescriptions of FIGS. 1 and 2, the numerous valves, temperature sensors,electronic controllers, and the like that may be employed and well-knownto a person of ordinary skill in the art are not included. Further,accompanying components that are often included in typical chemicalprocessing operations, carrier gas supply systems, pumps, compressors,furnaces, or other subsystems are not depicted. It should be understoodthat these components are within the spirit and scope of the presentembodiments disclosed. However, operational components, such as thosedescribed in the present disclosure, may be added to the embodimentsdescribed in the present disclosure.

Arrows in the drawings refer to process streams. However, the arrows mayequivalently refer to transfer lines, which may serve to transferprocess streams between two or more system components. Additionally,arrows that connect to system components may define inlets or outlets ineach given system component. The arrow direction corresponds generallywith the major direction of movement of the materials of the streamcontained within the physical transfer line signified by the arrow.Furthermore, arrows that do not connect two or more system componentsmay signify a product stream that exits the depicted system or a systeminlet stream that enters the depicted system. Product streams may befurther processed in accompanying chemical processing systems or may becommercialized as end products.

Additionally, arrows in the drawings may schematically depict processsteps of transporting a stream from one system component to anothersystem component. For example, an arrow from one system componentpointing to another system component may represent “passing” a systemcomponent effluent to another system component, which may include thecontents of a process stream “exiting” or being “removed” from onesystem component and “introducing” the contents of that product streamto another system component.

Reference will now be made in greater detail to various embodiments,some embodiments of which are illustrated in the accompanying drawings.

DETAILED DESCRIPTION

The present disclosure is directed to an isomerization catalyst andmethods of producing the isomerization catalyst. In particular, thepresent disclosure is directed to methods of producing an isomerizationcatalyst through the hydrothermal synthesis of magnesium oxide. Thepresent disclosure is also directed to methods of producing 1-butenefrom a 2-butene-containing feedstock through isomerization with theisomerization catalyst of the present disclosure. In particular, thepresent disclosure is directed to methods of producing 1-butene from a2-butene-containing feedstock that include contacting the2-butene-containing feedstock with the isomerization catalyst made bythe synthesis methods of the present disclosure to produce anisomerization reaction effluent that includes at least 1-butene. Theisomerization catalyst produced by the methods of the present disclosuremay have increased thermal stability, which may result in a reduceddeactivation rate of the isomerization catalyst at temperaturessufficient to produce 1-butene from the isomerization of 2-butene.Accordingly, systems incorporating the isomerization catalyst producedby the present disclosure may have increased efficiency, an increasedconversion rate of 2-butene, and a greater yield of 1-butene.

As used throughout the present disclosure, the term “butene” or“butenes” may refer to compositions comprising one or more than one of1-butene, trans-2-butene, cis-2-butene, isobutene, or mixtures of theseisomers. As used throughout the present disclosure, the term “normalbutenes” may refer to compositions comprising one or more than one of1-butene, trans-2-butene, cis-2-butene, or mixtures of these isomers,and are substantially free of isobutene. As used in the presentdisclosure, the term “2-butene” may refer to trans-2-butene,cis-2-butene, or a mixture of these two isomers. As used in the presentdisclosure, the term “substantially free” of a component means less than1 wt. % of that component in a particular portion of a catalyst, stream,or reaction zone. For example, a composition, which may be substantiallyfree of isobutene, may comprise less than 1 wt. % of isobutene.

As shown in Reaction 1 (RXN 1), the isomerization of 2-butene to1-butene, and the isomerization of 1-butene to 2-butene, is anequilibrium reaction, as denoted by the bi-directional arrows withsingle heads. The isomerization of 2-butene and 1-butene may be achievedwith an isomerization catalyst. As used in the present disclosure, theterm “isomerization catalyst” may refer to a catalyst that promotesisomerization of alkenes, including, for example, isomerization of2-butenes to 1-butene. Referring to RXN 1, the isomerization reaction isnot limited to these reactants and products; however, RXN 1 provides asimplified illustration of the reaction methodology.

In operation, a product stream comprising 1-butene may be produced froma feedstock containing 2-butene through isomerization by contacting thefeedstock with an isomerization catalyst. Optionally, the isomerizationreaction effluent, may be further processed, such as being contactedwith a metathesis catalyst, a cracking catalyst, or both, to furtherutilize the 1-butene produced. The feedstock may comprise 1-butene,trans-2-butene, cis-2-butene, or combinations of these. The feedstockmay further comprise other C₁-C₆ components. The presence of isobuteneand other inert gases or non-olefinic hydrocarbons, such as n-butane, inthe feedstock do not negatively affect the target isomerizationreactions, and the amount of any side products formed as a result oftheir presence in the feedstock do not affect the overall yield of1-butene. Although described in the present disclosure in the context ofconducting isomerization between 2-butene and 1-butene, it is understoodthat the isomerization catalysts of the present disclosure and systemsand methods of conducting isomerization using the isomerizationcatalysts may be useful for conducting other isomerization, such asisomerizations between other olefins, or for conducting other functions,such as removing contaminants from a feed stream, for example.

Referring now to FIG. 1, a system for producing 1-butene from afeedstock containing 2-butene is depicted, the system being designatedby reference number 100. The system 100 may include an isomerizationreaction zone 110 or a plurality of isomerization reaction zones. Theone or isomerization reaction zones may be disposed within a singlereactor 120 or in multiple reactors, which may be in series or inparallel. As depicted in FIG. 1, a feedstock 130 may be introduced intothe reactor 120, and an isomerization reaction effluent 140 may bepassed out of the reactor 130. Accordingly, the feedstock 130 may beintroduced into the reactor 120, passed through the isomerizationreaction zone 110, and passed out of the reactor 120 as theisomerization reaction effluent 140.

As described previously in the present disclosure, the feedstock 130 maycomprise 1-butene, cis-2-butene, trans-2-butene, or combinations ofthese. The feedstock 130 may comprise from 10 wt. % to 60 wt. % 1-butenebased on the total weight of the feedstock 130. For example, thefeedstock 130 may comprise from 10 wt. % to 50 wt. %, from 10 wt. % to40 wt. %, from 10 wt. % to 30 wt. %, from 10 wt. % to 20 wt. %, from 20wt. % to 60 wt. %, from 20 wt. % to 50 wt. %, from 20 wt. % to 40 wt. %,from 20 wt. % to 30 wt. %, from 30 wt. % to 60 wt. %, from 30 wt. % to50 wt. %, from 30 wt. % to 40 wt. %, from 40 wt. % to 60 wt. %, from 40wt. % to 50 wt. %, or from 50 wt. % to 60 wt. % 1-butene based on thetotal weight of the feedstock 130. The feedstock 130 may comprise from10 wt. % to 100 wt. % 2-butene (that is, cis-2-butene, trans-2-butene,or both) based on the total weight of the feedstock 130. For example,the feedstock 130 may comprise from 10 wt. % to 80 wt. %, from 10 wt. %to 60 wt. %, from 10 wt. % to 40 wt. %, from 10 wt. % to 20 wt. %, from20 wt. % to 100 wt. %, from 20 wt. % to 80 wt. %, from 20 wt. % to 60wt. %, from 20 wt. % to 40 wt. %, from 40 wt. % to 100 wt. %, from 40wt. % to 80 wt. %, from 40 wt. % to 60 wt. %, from 60 wt. % to 100 wt.%, from 60 wt. % to 80 wt. %, or from 80 wt. % to 100 wt. % 2-butenebased on the total weight of the feedstock 130. Additionally, thefeedstock 130 may be substantially free of ethylene.

The feedstock 130 may comprise a raffinate stream. As used in thepresent disclosure, the term “raffinate” may refer to the residue C₄stream from a naphtha cracking process or from a gas cracking processwhen components are removed (the C₄ stream typically containing, as itsprimary components, n-butane, 1-butene, 2-butene, isobutene, and1,3-butadiene, and optionally some isobutane and said primary componentstogether forming up to 99% or more of the C₄ stream). The feedstock 130may comprise a raffinate-1 stream. As used in the present disclosure,the term “raffinate-1” may refer to the C₄ residual obtained afterseparation of 1,3-butadiene from a raffinate stream, and comprisesmainly 2-butene, 1-butene, and isobutene, which may make up greater thanor equal to 55 wt. % of the raffinate-1 stream. For example, theraffinate-1 stream may comprise from 10 wt. % to 30 wt. % of 2-butene,from 25 wt. % to 50 wt. % of 1-butene, and from 20 wt. % to 50 wt. %isobutene, based on the total weight of the raffinate-1 stream. Thefeedstock 130 may comprise a raffinate-2 stream. As used in the presentdisclosure, the term “raffinate-2” may refer to the C₄ residual obtainedafter separation of 1,3-butadiene and isobutene from a raffinate stream,and comprises mainly 2-butene, 1-butene, and n-butane, which may make upgreater than or equal to 45 wt. % of the raffinate-2 stream. Forexample, the raffinate-2 stream may comprise from 20 wt. % to 60 wt. %of 2-butene, from 10 wt. % to 60 wt. % of 1-butene, and from 15 wt. % to25 wt. % n-butane, based on the total weight of the raffinate-2 stream.The feedstock 130 may comprise a raffinate-3 stream. As sued in thepresent disclosure, the term “raffinate-3” may refer to the C₄ residualobtained after separation of 1,3-butadiene, isobutene, and 1-butene fromthe C₄ raffinate stream, and comprises mainly 2-butene, n-butane, andunseparated 1-butene, which may make up greater than or equal to 40 wt.% of the raffinate-3 stream. For example, the raffinate-3 stream maycomprise from 30 wt. % to 70 wt. % of 2-butene and from 10 wt. % to 30wt. % of n-butane, based on the total weight of the raffinate-3 stream.

The isomerization reaction zone 110 may be maintained at anisomerization reaction temperature sufficient to promote theisomerization reactions between 2-butene and 1-butene in the feedstock130. The isomerization reaction temperature may be from 300 degreesCelsius (° C.) to 600° C. For example, the isomerization reactiontemperature may be from 300° C. to 550° C., from 300° C. to 500° C.,from 300° C. to 450° C., from 300° C. to 400° C., from 300° C. to 350°C., from 350° C. to 600° C., from 350° C. to 550° C., from 350° C. to500° C., from 350° C. to 450° C., from 350° C. to 400° C., from 400° C.to 600° C., from 400° C. to 550° C., from 400° C. to 500° C., from 400°C. to 450° C., from 450° C. to 600° C., from 450° C. to 550° C., from450° C. to 500° C., from 500° C. to 600° C., from 500° C. to 550° C., orfrom 550° C. to 600° C. These temperature ranges may be sufficient topromote the isomerization reactions and, in particular, may besufficient to promote the isomerization of 2-butene to 1-butene. Withoutbeing bound by any particular theory, it is believed that thesetemperature ranges may shift the equilibrium of the isomerizationreactions between 2-butene and 1-butene, such that the production of1-butene is favored. Conversely, temperatures less than thesetemperature ranges may shift the equilibrium of the isomerizationreactions between 2-butene and 1-butene, such that the production of2-butene is favored. Accordingly, these temperature ranges may increasethe yield of 1-butene by system 100.

Referring still to FIG. 1, the isomerization reaction zone 110 of thesystem 100 may include an isomerization catalyst 112. The isomerizationcatalyst 112 may be a magnesium oxide (MgO) catalyst. The isomerizationcatalyst 112 may promote equilibration of the isomerization reactionsbetween the 2-butene and 1-butene in the feedstock 130. When thefeedstock 130 has a concentration of 2-butene greater than theequilibration concentration of 2-butene, the isomerization catalyst 112may isomerize at least a portion of the 2-butene to 1-butene.Conversely, when the feedstock 130 has a concentration of 1-butenegreater than the equilibrium concentration of 1-butene, theisomerization catalyst 112 may isomerize at least a portion of the1-butene to 2-butene. As described previously, the isomerizationcatalyst 112 may also shift the equilibrium of the isomerizationreactions between 2-butene and 1-butene, such that the production of1-butene is favored at equilibrium, or such that the production of2-butene is favored at equilibrium, based on the operating conditions ofthe system 100. For example, at temperatures greater than 300° C., theisomerization catalyst 112 may shift the equilibrium of theisomerization reactions between 2-butene and 1-butene, such that theproduction of 1-butene is favored at equilibrium. Conversely, attemperatures less than 300° C., the isomerization catalyst 112 may shiftthe equilibrium of the isomerization reactions between 2-butene and1-butene, such that the production of 2-butene is favored atequilibrium. The isomerization reaction zone 110 may produce anisomerization effluent that may comprise 1-butene, cis-2-butene,trans-2-butene, or combinations of these.

As described previously in the present disclosure,commercially-available magnesium oxide catalysts may have poor catalyticactivity, inferior thermal stability, or both, which may result in adecreased yield of 1-butene. Accordingly, the isomerization catalyst 112of the present disclosure may be prepared using a hydrothermal synthesismethod. The resulting isomerization catalyst 112 may have increasedthermal stability and catalytic activity compared tocommercially-available magnesium oxide catalysts. During hydrothermalsynthesis, the isomerization catalyst may be synthesized from thereaction of a magnesium precursor, such as but not limited to magnesiumnitrate hexahydrate, and a hydrolyzing agent, such as but not limited tourea, in an aqueous solution. The aqueous solution may then behydrothermally treated in order to produce a magnesium oxideprecipitant. The magnesium oxide resulting from the reaction takingplace during the hydrothermal treatment may precipitate out of theaqueous solution as a white solid, which may then be separated, washed,dried, and calcined. The isomerization catalyst 112 may also be preparedusing a surfactant-assisted hydrothermal synthesis method, in which theaqueous solution further comprises a surfactant, such as cetrimoniumbromide (CTAB), in an aqueous solution. The inclusion of a surfactantmay increase the surface area and cumulative volume of pores and reducethe average particle size of the resulting magnesium oxide.

As described previously in the present disclosure, the aqueous solutionused in the hydrothermal synthesis may comprise a magnesium precursorand a hydrolyzing agent. The magnesium precursor may be selected fromone or more of magnesium nitrate hexahydrate, magnesium acetatetetrahydrate, and magnesium chloride tetrahydrate. The hydrolyzing agentmay be selected from one or more of urea, a diamine, such as ethylenediamine, and ammonium hydroxide. The aqueous solution used in thehydrothermal synthesis may comprise the magnesium precursor and thehydrolyzing agent in a molar ratio of from 1:10 to 1:1. For example, theaqueous solution used in the hydrothermal synthesis may comprise themagnesium precursor and the hydrolyzing agent in a molar ratio of from1:10 to 1:2, from 1:10 to 1:3, from 1:10 to 1:4, from 1:10 to 1:5, from1:10 to 1:6, from 1:10 to 1:7, from 1:10 to 1:8, from 1:10 to 1:9, from1:9 to 1:1, from 1:9 to 1:2, from 1:9 to 1:3, from 1:9 to 1:4, from 1:9to 1:5, from 1:9 to 1:6, from 1:9 to 1:7, from 1:9 to 1:8, from 1:8 to1:1, from 1:8 to 1:2, from 1:8 to 1:3, from 1:8 to 1:4, from 1:8 to 1:5,from 1:8 to 1:6, from 1:8 to 1:7, from 1:7 to 1:1, from 1:7 to 1:2, from1:7 to 1:3, from 1:7 to 1:4, from 1:7 to 1:5, from 1:7 to 1:6, from 1:6to 1:1, 1:6 to 1:2, from 1:6 to 1:3, from 1:6 to 1:4, from 1:6 to 1:5,from 1:5 to 1:1, from 1:5 to 1:2, from 1:5 to 1:3, from 1:5 to 1:4, from1:4 to 1:1, from 1:4 to 1:2, from 1:4 to 1:3, from 1:3 to 1:1, from 1:3to 1:2, or from 1:2 to 1:1. Without being bound by any particulartheory, it is believed that the hydrolyzing agent may increase the yieldof magnesium oxide during the hydrothermal synthesis by improving theseeding effect and crystallization of magnesium oxide duringprecipitation. For example, when the aqueous solution used in thehydrothermal synthesis comprises the magnesium precursor and thehydrolyzing agent in a molar ratio less than 1:10, the yield of themagnesium oxide, and the isomerization catalyst, may be reduced. Thisreduced yield may render the process unsuitable for the production ofthe isomerization catalyst on an industrial scale.

As described previously in the present disclosure, the aqueous solutionused in the hydrothermal synthesis may further comprise cetrimoniumbromide. The aqueous solution used in the hydrothermal synthesis maycomprise the magnesium precursor and cetrimonium bromide in a molarratio of from 1:0.1 to 1:0.01. For example, the aqueous solution used inthe hydrothermal synthesis may comprise the magnesium precursor andcetrimonium bromide in a molar ratio of from 1:0.1 to 1:0.02, from 1:0.1to 1:0.03, from 1:0.1 to 1:0.04, from 1:0.1 to 1:0.05, from 1:0.1 to1:0.06, from 1:0.1 to 1:0.07, from 1:0.1 to 1:0.08, from 1:0. 1 to1:0.09, from 1:0.09 to 1:0.01, from 1:0.09 to 1:0.02, from 1:0.09 to1:0.03, from 1:0.09 to 1:0.04, from 1:0.09 to 1:0.05, from 1:0.09 to1:0.06, from 1:0.09 to 1:0.07, from 1:0.09 to 1:0.08, from 1:0.08 to1:0.01, from 1:0.08 to 1:0.02, from 1:0.08 to 1:0.03, from 1:0.08 to1:0.04, from 1:0.08 to 1:0.05, from 1:0.08 to 1:0.06, from 1:0.08 to1:0.07, from 1:0.07 to 1:0.01, from 1:0.07 to 1:0.02, from 1:0.07 to1:0.03, from 1:0.07 to 1:0.04, from 1:0.07 to 1:0.05, from 1:0.07 to1:0.06, from 1:0.06 to 1:0.01, 1:0.06 to 1:0.02, from 1:0.06 to 1:0.03,from 1:0.06 to 1:0.04, from 1:0.06 to 1:0.05, from 1:0.05 to 1:0.01,from 1:0.05 to 1:0.02, from 1:0.05 to 1:0.03, from 1:0.05 to 1:0.04,from 1:0.04 to 1:0.01, from 1:0.04 to 1:0.02, from 1:0.04 to 1:0.03,from 1:0.03 to 1:0.01, from 1:0.03 to 1:0.02, or from 1:0.02 to 1:0.01.Without being bound by any particular theory, it is believed thatcetrimonium bromide may act as a surface directing agent duringhydrothermal synthesis, affecting the mesoporosity of the resultingmagnesium oxide and, as a result, the surface area and pore volume ofthe isomerization catalyst. For example, when the aqueous solution usedin the hydrothermal synthesis comprises the magnesium precursor andcetrimonium bromide in a molar ratio less than 1:0.1, the surface areaand pore volume of the resulting isomerization catalyst may be reduced,resulting in a decrease in catalytic activity.

The pH of the aqueous solution used in the hydrothermal synthesis may beadjusted such that the aqueous solution is more acidic or more basic.The pH of the aqueous solution used in the hydrothermal synthesis may beadjusted such that the pH of the aqueous solution is from 3 to 7. Forexample, the pH of the aqueous solution used in the hydrothermalsynthesis may be adjusted such that the pH of the aqueous solution isfrom 3 to 6, from 3 to 5, from 3 to 4, from 4 to 7, from 4 to 6, from 4to 5, from 5 to 7, from 5 to 6, or from 6 to 7. In embodiments, the pHof the aqueous solution used in the hydrothermal synthesis may beadjusted such that the pH of the aqueous solution is from 8 to 12. Forexample, the pH of the aqueous solution used in the hydrothermalsynthesis may be adjusted such that the pH of the aqueous solution isfrom 8 to 11, from 8 to 10, from 8 to 9, from 9 to 12, from 9 to 11,from 9 to 10, from 10 to 12, from 10 to 11, or from 11 to 12. Withoutbeing bound by any particular theory, it is believed that the pH of theaqueous solution may affect the yield of the isomerization catalyst, themorphology of the isomerization catalyst, or both. For example, acidicor basic aqueous solutions may result in the increased precipitation ofmagnesium oxide during hydrothermal synthesis and, as a result, increasethe yield of the isomerization catalysts. Additionally, the morphologyof the isomerization catalyst, which may increase or decrease thecatalytic activity, may be determined by the presence of anionic andcationic species within the aqueous solution. In particular, the anionicand cationic species, the concentration of which increases with theacidity or basicity of the aqueous solution, may be responsible forstearic hindrance during hydrothermal synthesis. Such stearic hindrancemay affect the morphology of the resulting magnesium oxide and, as aresult, increase the catalytic activity of the isomerization catalyst.

As described previously in the present disclosure, the aqueous solutionmay be hydrothermally treated in order to produce a magnesium oxideprecipitant. The hydrothermal treatment may comprise the heating of theaqueous solution. The heating of the aqueous solution may be conductedin a pressure vessel, such as an autoclave. The hydrothermal treatmentof the aqueous solution may comprise heating the aqueous solution to atemperature sufficient to cause the reaction of the magnesium precursorand the hydrolyzing agent, resulting in the precipitation of magnesiumoxide from the aqueous solution. The hydrothermal treatment of theaqueous solution may comprise heating the aqueous solution to atemperature of from 100° C. to 140° C. For example, the hydrothermaltreatment of the aqueous solution may comprise heating the aqueoussolution to a temperature of from 100° C. to 135° C., from 100° C. to130° C., from 100° C. to 125° C., from 100° C. to 120° C., from 100° C.to 115° C., from 100° C. to 110° C., from 100° C. to 105° C., from 105°C. to 140° C., from 105° C. to 135° C., from 105° C. to 130° C., from105° C. to 125° C., from 105° C. to 120° C., from 105° C. to 115° C.,from 105° C. to 110° C., from 110° C. to 140° C., from 110° C. to 135°C., from 110° C. to 130° C., from 110° C. to 125° C., from 110° C. to120° C., from 110° C. to 115° C., from 115° C. to 140° C., from 115° C.to 135° C., from 115° C. to 130° C., from 115° C. to 125° C., from 115°C. to 120° C., from 120° C. to 140° C., from 120° C. to 135° C., from120° C. to 130° C., from 120° C. to 125° C., from 125° C. to 140° C.,from 125° C. to 135° C., from 125° C. to 130° C., from 130° C. to 140°C., from 130° C. to 135° C., or from 135° C. to 140° C.

The hydrothermal treatment of the aqueous solution may comprise heatingthe aqueous solution for an amount of time sufficient to cause thereaction of the magnesium precursor and the hydrolyzing agent, resultingin the precipitation of magnesium oxide from the aqueous solution. Inembodiments, the hydrothermal treatment of the aqueous solution maycomprise heating the aqueous solution for a duration of from 48 hours to96 hours. For example, the hydrothermal treatment of the aqueoussolution may comprise heating the aqueous solution for a duration offrom 48 hours to 84 hours, from 48 hours to 72 hours, from 48 hours to60 hours, from 60 hours to 96 hours, from 60 hours to 84 hours, from 60hours to 72 hours, from 72 hours to 96 hours, from 72 hours to 84 hours,or from 84 hours to 96 hours.

As described previously in the present disclosure, after hydrothermaltreatment the precipitated magnesium oxide may be separated, washed,dried, and calcined to produce the isomerization catalyst 112. Withoutbeing bound by any particular theory, it is believed that thecalcination of the magnesium oxide to produce the isomerization catalyst112 may activate the reaction sites for butene isomerization. Magnesiumoxide is generally basic in nature and the basicity of the magnesiumoxide may be influenced by the calcination temperature and process.Calcination conditions may influence the strength and quantity of basicreaction sites in the isomerization catalyst 112. Selection of theappropriate calcination temperature may enhance the number and strengthof the basic sites in the magnesium oxide, thus, enhancing theisomerization performance of the isomerization catalyst 112. The“calcination temperature” is a target average temperature to which themagnesium oxide is heated and at which the magnesium oxide is calcinedover a period of time during the calcination process. The “rampingrate,” as used in the present disclosure, is a rate at which thetemperature of the magnesium oxide is increased from a startingtemperature to the calcination temperature. The magnesium oxide may beplaced in the calcination oven and the temperature of the calcinationoven may be increased at the ramping rate to the calcinationtemperature. Then, the magnesium oxide may be maintained at thecalcination temperature for a predetermined period of time. At the endof the predetermined period of time, the calcined magnesium oxide may beallowed to slowly cool down to ambient temperature. Optionally, theisomerization catalyst may be calcined a second time. The calcinationtemperature, ramping rate, and duration of the second calcinationprocess may each be the same or different from the calcinationtemperature, ramping rate, and duration of the first calcinationprocess.

The magnesium oxide may be calcined in a calcination oven at acalcination temperature of from 450° C. to 650° C. For example, themagnesium oxide may be calcined in a calcination oven at a calcinationtemperature of from 450° C. to 600° C., from 450° C. to 550° C., from450° C. to 500° C., from 500° C. to 650° C., from 500° C. to 600° C.,from 500° C. to 550° C., from 550° C. to 650° C., from 550° C. to 600°C., or from 600° C. to 650° C. The ramping rate of the calcinationprocess may be from 1 degree Celsius per minute (° C./min) to 4° C./min.For example, the ramping rate of the calcination process may be from 1°C./min to 3° C./min, from 1° C./min to 2.5° C./min, from 1° C./min to 2°C./min, from 1.5° C./min to 2° C./min, from 1.5° C./min to 4° C./min,from 1.5° C./min to 3° C./min, from 1.5° C./min to 2.5° C./min, from1.5° C./min to 2° C./min, from 2° C./min to 4° C./min, from 2° C./min to3° C./min, from 2° C./min to 2.5° C./min, from 2.5° C./min to 4° C./min,from 2.5° C./min to 3° C./min, or from 3° C./min to 4° C./min. Themagnesium oxide may be calcined in the calcination oven for a durationof from 1 hour to 10 hours. For example, the magnesium oxide may becalcined in the calcination oven for a duration of from 1 hour to 8hours, from 1 hour to 6 hours, from 1 hour to 4 hours, from 1 hour to 2hours, from 2 hours to 10 hours, from 2 hours to 8 hours, from 2 hoursto 6 hours, from 2 hours to 4 hours, from 4 hours to 10 hours, from 4hours to 8 hours, from 4 hours to 6 hours, from 6 hours to 10 hours,from 6 hours to 8 hours, or from 8 hours.

The isomerization catalyst 112 resulting from the process of the presentdisclosure may have a surface area of from 100 square meters per gram(m²/g) to 300 m²/g, as determined by the Brunauer Emmett-Teller (BET)method. For example, the isomerization catalyst 112 may have a surfacearea of from 100 m²/g to 275 m²/g, from 100 m²/g to 250 m²/g, from 100m²/g to 225 m²/g, from 100 m²/g to 200 m²/g, from 100 m²/g to 175 m²/g,from 100 m²/g to 150 m²/g, from 100 m²/g to 125 m²/g, from 125 m²/g to300 m²/g, from 125 m²/g to 275 m²/g, from 125 m²/g to 250 m²/g, from 125m²/g to 225 m²/g, from 125 m²/g to 200 m²/g, from 125 m²/g to 175 m²/g,from 125 m²/g to 150 m²/g, from 150 m²/g to 300 m²/g, from 150 m²/g to275 m²/g, from 150 m²/g to 250 m²/g, from 150 m²/g to 225 m²/g, from 150m²/g to 200 m²/g, from 150 m²/g to 175 m²/g, from 175 m²/g to 300 m²/g,from 175 m²/g to 275 m²/g, from 175 m²/g to 250 m²/g, from 175 m²/g to225 m²/g, from 175 m²/g to 200 m²/g, from 200 m²/g to 300 m²/g, from 200m²/g to 275 m²/g, from 200 m²/g to 250 m²/g, from 200 m²/g to 225 m²/g,from 225 m²/g to 300 m²/g, from 225 m²/g to 275 m²/g, from 225 m²/g to250 m²/g, from 250 m²/g to 300 m²/g, from 250 m²/g to 275 m²/g, or from275 m²/g to 300 m²/g, as determined by the BET method.

The isomerization catalyst 12 resulting from the process of the presentdisclosure may have a cumulative pore volume of from 0.10 cubiccentimeters per gram (cm³/g) to 0.30 cm³/g, as determined by theBarrett, Joyner, and Halenda (BJH) method. For example, theisomerization catalyst 112 may have a cumulative pore volume of from0.10 cm³/g to 0.26 cm³/g, from 0.10 cm³/g to 0.22 cm³/g, from 0.10 cm³/gto 0.18 cm³/g, from 0.10 cm³/g to 0.14 cm³/g, from 0.14 cm³/g to 0.30cm³/g, from 0.14 cm³/g to 0.26 cm³/g, from 0.14 cm³/g to 0.22 cm³/g,from 0.14 cm³/g to 0.18 cm³/g, from 0.18 cm³/g to 0.30 cm³/g, from 0.18cm³/g to 0.26 cm³/g, from 0.18 cm³/g to 0.22 cm³/g, from 0.22 cm³/g to0.30 cm³/g, from 0.22 cm³/g to 0.26 cm³/g, or from 0.26 cm³/g to 0.30cm³/g, as determined by the BJH method.

The isomerization catalyst 112 resulting from the process of the presentdisclosure may have an average pore width of from 5 nanometers (nm) to10 nm, as determined by the BJH method. For example, the isomerizationcatalyst 112 may have an average pore width of from 5 nm to 9 nm, from 5nm to 8 nm, from 5 nm to 7 nm from 5 nm to 6 nm, from 6 nm to 10 nm,from 6 nm to 9 nm, from 6 nm to 8 nm, from 6 nm to 7 nm, from 7 nm to 10nm, from 7 nm to 9 nm, from 7 nm to 8 nm, from 8 nm to 10 nm, from 8 nmto 9 nm, or from 9 nm to 10 nm, as determined by the BJH method.

The isomerization catalyst 112 resulting from the process of the presentdisclosure may have an average particle size of from 20 nm to 50 nm, ascalculated by the Scherrer equation. For example, the isomerizationcatalyst 112 may have an average particle size of from 20 nm to 45 nm,from 20 nm to 40 nm, from 20 nm to 35 nm, from 20 nm to 30 nm, from 20nm to 25 nm, from 25 nm to 50 nm, from 25 nm to 45 nm, from 25 nm to 40nm, from 25 nm to 35 nm, from 25 nm to 30 nm, from 30 nm to 50 nm, from30 nm to 45 nm, from 30 nm to 40 nm, from 30 nm to 35 nm, from 35 nm to50 nm, from 35 nm to 45 nm, from 35 nm to 40 nm, from 40 nm to 50 nm,from 40 nm to 45 nm, or from 45 nm to 50 nm, as calculated by theScherrer equation.

The isomerization catalyst 112 having these properties (that is, thepreviously described surface area, cumulative pore volume, average porewidth, and average particle size) may have increased catalytic activityand thermal stability compared to commercially-available magnesium oxidecatalysts. As a result, the system 100 comprising the isomerizationcatalyst 112 may have an increased 1-butene yield compared to a systemutilizing a conventional magnesium oxide catalysts.

Referring now to FIG. 2, in embodiments, a fluid/solid separator 150 maybe disposed downstream of the isomerization reaction zone 110, upstreamof the isomerization reaction zone 110, or both. As used in the presentdisclosure, the term “fluid/solid separator” may refer to a fluidpermeable barrier between catalyst beds that reduces or prevents solidcatalyst particles in one catalyst bed from migrating from the reactionzone, while allowing for reactants and products to move through theseparator. The fluid/solid separator 150 may be chemically inert andgenerally makes no contribution to the reaction chemistry. Inserting thefluid/solid separator 150 upstream or downstream of the isomerizationreaction zone 110 may maintain the isomerization catalyst 112 in theisomerization reaction zone 110, and improve the isothermal stability ofthe isomerization reactions, which may lead to the decreased productionof undesired by-products and increased yield of 1-butene.

Referring again to FIG. 1, various operating conditions are contemplatedfor contacting the feedstock 130 with the isomerization catalyst 112 inthe isomerization zone 110. In embodiments, the feedstock 130 maycontact the isomerization catalyst 112 in the isomerization zone 110 ata space hour velocity of from 10 per hour (h⁻¹) to 10,000 h⁻¹. Forexample, the feedstock 130 may contact the isomerization catalyst 112 inthe isomerization zone 110 at a space hour velocity of from 10 h⁻¹ to5000 h⁻¹, from 10 h⁻¹ to 2500 h⁻¹, from 10 h⁻¹ to 1200 h⁻¹, from 100 h⁻¹to 10,000 h⁻¹, from 100 h⁻¹ to 5000 h⁻¹, from 100 h⁻¹ to 2500 h⁻¹, from100 h⁻¹ to 1200 h⁻¹, from 300 ⁻¹ to 10,000 h⁻¹, from 300 h⁻¹ to 5000h⁻¹, from 300 h⁻¹ to 2500 h⁻¹, from 300 h⁻¹ to 1200 h⁻¹, from 500 h⁻¹ to10,000 h⁻¹, from 500 h⁻¹ to 5000 h⁻¹, from 500 h⁻¹ to 2500 h⁻¹, or from500 h⁻¹ to 1200 h⁻¹. Furthermore, the feedstock 130 may contact theisomerization catalyst 112 in the isomerization zone 110 at a pressureof from 1 bar to 30 bars. For example, the feedstock 130 may contact theisomerization catalyst 112 in the isomerization zone 110 at a pressureof from 1 bar to 20 bars, from 1 bar to 10 bars, from 2 bars to 30 bars,from 2 bars to 20 bars, or from 2 bars to 10 bars. The feedstock 130 mayalso contact the isomerization catalyst 112 in the isomerization zone110 at atmospheric pressure.

Optionally, prior to the introduction of the feedstock 130 to the system100, the isomerization catalyst 112 may be pretreated. For example, theisomerization catalyst 112 in the system 100 may be pretreated bypassing a heated gas stream through the isomerization catalyst 112 for apretreatment period. The gas stream may include one or more of anoxygen-containing gas, nitrogen gas (N₂), carbon monoxide (CO), hydrogengas (H₂), a hydrocarbon gas, air, other inert gas, or combinations ofthese gases. The temperature of the heated gas stream may be from 250°C. to 700° C., from 250° C. to 650° C., from 250° C. to 600° C., from250° C. to 500° C., from 300° C. to 700° C., from 300° C. to 650° C.,from 300° C. to 600° C., from 300° C. to 500° C., from 400° C. to 700°C., from 400° C. to 650° C., from 400° C. to 600° C., or from 400° C. to500° C. The pretreatment period may be from 1 minute to 30 hours, from 1minute to 20 hours, from 1 minute to 10 hours, from 1 minute to 5 hours,from 0.5 hours to 30 hours, from 0.5 hours to 20 hours, from 0.5 hoursto 10 hours, from 0.5 hours to 5 hours, from 1 hours to 30 hours, from 1hour to 20 hours, from 1 hour to 10 hours, from 1 hour to 5 hours, from5 hours to 30 hours, from 5 hours to 20 hours, or from 5 hours to 10hours. For example, the isomerization catalyst 112 in the system 100 maybe pretreated with nitrogen gas at a temperature of 550° C. for apretreatment period of from 1 hour to 5 hours before introducing thefeedstock 130.

EXAMPLES

The various embodiments of isomerization catalysts, methods of makingthe isomerization catalysts, and methods of using the isomerizationcatalyst in the production of 1-butene will be further clarified by thefollowing examples. The examples are illustrative in nature, and shouldnot be understood to limit the subject matter of the present disclosure.

Example 1 Hydrothermal Synthesis of Isomerization Catalyst

An isomerization catalyst was prepared using hydrothermal synthesis. Inparticular, 18.02 grams (g) of urea and 15.39 g of magnesium nitratehexahydrate (Mg(NO₃)₂.6H₂O) were dissolved in 100 milliliters (mL) ofdeionized water (DI water) and stirred vigorously at room temperaturefor 1 hour to form a catalyst precursor solution. The catalyst precursorsolution was then transferred to an autoclave and placed in an oven at120° C. for 72 hours at a ramp rate of 1 degree Celsius per minute (°C./min). The resulting magnesium oxide precipitants were then filteredfrom the solution via vacuum filtration, dried overnight at roomtemperature, and them dried in a vacuum oven at 80° C. for 24 hours toform an isomerization catalyst. The isomerization catalyst was thencalcined in a calcination oven under air at a ramping rate of 1° C./minuntil the isomerization catalyst attained a temperature of 550° C. Theisomerization catalyst was then maintained in the calcination oven at atemperature of 550° C. for 5 hours. Following calcination, theisomerization catalyst was maintained in the calcination oven andallowed to slowly cool to room temperature. The isomerization catalystprepared according to the above-described method is referred tosubsequently as the catalyst of Example 1.

Example 2 Surfactant-Assisted Hydrothermal Synthesis of IsomerizationCatalyst

An isomerization catalyst was prepared using surfactant-assistedhydrothermal synthesis. In particular, 18.02 g of urea and 15.39 g ofmagnesium nitrate hexahydrate were dissolved in 100 mL of deionizedwater and rapidly stirred at room temperature for 1 hour to form a firstsolution. Cetrimonium bromide (CTAB) was then added to the firstsolution such that the molar ratio of magnesium to cetrimonium bromidein the first solution was 1:0.03, and the first solution was stirred atroom temperature for 2 hours to form a catalyst precursor solution. Thecatalyst precursor solution was then then processed according to thesame procedure previously described in Example 1 to form anisomerization catalyst. The isomerization catalyst prepared according tothe above-described method is referred to subsequently as the catalystof Example 2.

Example 3 Surfactant-Assisted Hydrothermal Fabrication of IsomerizationCatalyst with pH Adjustment

An isomerization catalyst was prepared using surfactant-assistedhydrothermal synthesis. In particular, 18.02 g of urea and 15.39 g ofmagnesium nitrate hexahydrate were dissolved in 100 mL of deionizedwater and rapidly stirred at room temperature for 1 hour to form a firstsolution. Next, 0.984 g of cetrimonium bromide was added to the firstsolution, which was then stirred at room temperature for 2 hours to forma catalyst precursor solution. The pH of the catalyst precursor solutionwas then adjusted to a pH of 5 by the dropwise addition of acetic acid.The catalyst precursor solution was then then processed according to thesame procedure previously described in Example 1 to form anisomerization catalyst. The isomerization catalyst prepared according tothe above-described method is referred to subsequently as the catalystof Example 3.

Example 4 Surfactant-Assisted Hydrothermal Fabrication of IsomerizationCatalyst with pH Adjustment

An isomerization catalyst was prepared using surfactant-assistedhydrothermal synthesis. In particular, 18.02 g of urea and 15.39 g ofmagnesium nitrate hexahydrate were dissolved in 100 mL of deionizedwater and rapidly stirred at room temperature for 1 hour to form a firstsolution. Next, 0.984 g of cetrimonium bromide was added to the firstsolution, which was then stirred at room temperature for 2 hours to forma catalyst precursor solution. The pH of the catalyst precursor solutionwas then adjusted to a pH of 9 by the dropwise addition of concentratedammonium. The catalyst precursor solution was then then processedaccording to the same procedure previously described in Example 1 toform an isomerization catalyst. The isomerization catalyst preparedaccording to the above-described method is referred to subsequently asthe catalyst of Example 4.

Example 5 Surfactant-Assisted Hydrothermal Fabrication of IsomerizationCatalyst with pH Adjustment

An isomerization catalyst was prepared using surfactant-assistedhydrothermal synthesis. In particular, 18.02 g of urea and 15.39 g ofmagnesium nitrate hexahydrate were dissolved in 100 mL of deionizedwater and rapidly stirred at room temperature for 1 hour to form a firstsolution. Next, 0.984 g of cetrimonium bromide was added to the firstsolution, which was then stirred at room temperature for 2 hours to forma catalyst precursor solution. The pH of the catalyst precursor solutionwas then adjusted to a pH of 11 by the dropwise addition of concentratedammonium. The catalyst precursor solution was then then processedaccording to the same procedure previously described in Example 1 toform an isomerization catalyst. The isomerization catalyst preparedaccording to the above-described method is referred to subsequently asthe catalyst of Example 5.

Comparative Example 6 Commercially-Available Magnesium Oxide Catalyst

An isomerization catalysts was prepared from a magnesium oxide basematerial, commercially available from Sigma Aldrich. Thecommercially-available magnesium oxide was dried overnight in a vacuumoven at 90° C. to form an isomerization catalyst. The isomerizationcatalyst was then calcined in a calcination oven under air at a rampingrate of 1° C./min until the isomerization catalyst attained atemperature of 550° C. The isomerization catalyst was then maintained inthe calcination oven at a temperature of 550° C. for 5 hours. Followingcalcination, the isomerization catalyst was maintained in thecalcination oven and allowed to slowly cool to room temperature. Theisomerization catalyst prepared according to the above-described methodis referred to subsequently as the catalyst of Comparative Example 6.

Example 7 Evaluation of Isomerization Catalyst Structures

The crystallographic structures of the catalysts of Examples 1-5 wereobtained from the measured XRD profiles of the catalysts. The XRDprofiles of the catalyst of Example 1 (360), the catalyst of Example 2(350), the catalyst of Example 3 (340), the catalyst of Example 4 (330),the catalyst of Example 5 (320), and the catalyst of Comparative Example6 (310) are depicted in FIG. 3. The diffraction peaks corresponding tothe cubic structure of magnesium oxide in a single phase may be observedin FIG. 3 at 2 Theta (2θ)=36 degrees (°), 42°, 62°, 74°, and 78° for allexamples. A comparison of the XRD profile of the commercially-availablemagnesium oxide catalyst with the XRD profiles of the catalysts ofExamples 1-5 also indicates that the average particle size of thecatalysts of Examples 1-5, as estimated by the Scherrer equation, aremuch smaller than the average particle size of the catalyst ofComparative Example 6. Additionally, a comparison of the XRD profiles ofthe catalysts of Examples 2-5 also indicates that the pH of the catalystprecursor solution has a negligible effect, if any, on the averageparticle size of the catalysts.

Example 8 Evaluation of Catalyst Properties

The mechanical properties of the catalysts of Examples 1-5, as well asthe catalyst of Comparative Example 6, were determined and provided inTable 1. In particular, the surface areas of the catalysts weredetermined by the Brunauer Emmett-Teller (BET) method, the cumulativevolume of pores and the average pore width were determined by theBarrett, Joyner, and Halenda (BJH) method, and the average particlesizes were calculated by the Scherrer equation. The properties of thecatalysts of Examples 1-5 and the catalyst of Comparative Example 6 areprovided in Table 1.

TABLE 1 Catalyst Properties Cumulative Average Average Surface VolumePore Particle Area of Pores Width Size Catalyst (m²/g) (cm³/g) (Å) (Å)Commercially-Available 60.49 0.30 184.41 991.91 Magnesium Oxide Example1 124.47 0.22 70.35 482.06 Example 2 175.30 0.18 55.27 342.66 Example 3262.55 0.41 64.23 228.53 Example 4 166.29 0.30 66.70 360.82 Example 5177.79 0.27 57.27 337.48

As shown by Table 1, the catalysts of Examples 1-5 had a significantlylarger surface area compared to the catalyst of Comparative Example 6.Moreover, the catalyst of Example 3, which was synthesized bysurfactant-assisted hydrothermal synthesis with a pH adjustment to a pHof 5, had the largest surface area of all the catalysts. As shown by theresults of Examples 9 and 10, the catalyst of Example 5 also resulted inone of the greatest 1-butene yields. This may suggest that the surfacearea of the catalysts may directly contribute to isomerization catalyticactivity. Similarly, the catalysts of Examples 1-5 had a significantlysmaller average particle compared to the catalyst of Comparative Example6. Moreover, the catalyst of Example 3 had the smallest average particlesize of all the catalysts. This may suggest that the average particlesize of the catalysts may directly contribute to isomerization catalyticactivity.

Example 9 Evaluation of Catalyst Performances at 300° C.

The catalysts of Examples 1-5, as well as the catalyst of ComparativeExample 6, were tested for activity and selectivity for isomerizing abutene-containing feed to 1-butene in a fixed-bed continuous flowreactor, such as the reactor depicted in FIG. 2, at atmosphericpressure. A fixed amount of 0.2 g of each catalyst was pressed andsieved to a desired particle size in the range of 212-300 microns (μm),and was packed into a reactor tube. Layers of silicon carbide werepositioned both upstream and downstream of the catalysts in order toensure that the catalysts remained within the desired isothermal range.

Each reactor was first heated to 120° C. under nitrogen at a flow rateof 120 milliliters per minute (mL/min) and argon at a flow rate of 6mL/min for 24 hours in order to ensure slow moisture desorption from thecatalysts and identify any potential gas leaks from the reactors. Thecatalysts were then activated under nitrogen at 550° C. and a flow rateof 120 mL/min for 12 hours. The reactors were then cooled to 300° C.under nitrogen before a feedstock of cis-2-butene was passed through thereactors at a flow rate of 0.008 grams per minute (g/min) and a weighthourly space velocity (WHSV) of 2.4 per hour (h⁻¹) for 18 hours.Quantitative analysis of the products for each reactor was performedusing a gas chromatograph (commercially available as Agilent GC-7890B)with a thermal conductivity detector (TCD) and two flame ionizationdetectors (FID).

The 1-butene yield (wt. %) as a function of time-on-stream (TOS) forreactors comprising the catalyst of Example 1 (420), the catalyst ofExample 2 (430), the catalyst of Example 3 (440), the catalyst ofExample 4 (450), the catalyst of Example 5 (460), and the catalyst ofComparative Example 6 (410) are depicted in FIG. 4. As shown by FIG. 4,there was a dramatic decrease in the isomerization catalytic activity inthe catalyst of Comparative Example 6 and the catalyst of Example 1within 10 hours. There was a similar decrease in isomerization catalyticactivity in the catalyst of Example 2 and the catalyst of Example 4, butboth catalysts were able to maintain a 1-butene yield of nearly 5 wt. %.Without being bound by any particular theory, it is believed that thismay be caused by the adsorption of water and oxygenates present in thefeedstock. Additionally, despite having the greatest surface area, thecatalyst of Example 1 appears to have the lowest isomerization catalyticactivity. Without being bound by any particular theory, it is believedthat this may be due to the formation of active surface sites havingreduced catalytic activity. Moreover, FIG. 4 shows that the catalysts ofExamples 3 and 5 maintain a significantly improved 1-butene yieldcompared to the other catalysts. This may indicate that adjusting the pHof the catalyst precursor solution to be weakly acidic (pH 5) orstrongly basic (pH 11) may improve the thermal stability of theresulting isomerization catalyst.

Example 10 Evaluation of Catalyst Performances at 400° C.

The catalysts of Examples 1-5, as well as the commercially-availablemagnesium oxide catalyst of Example 6, were tested again, according tothe same process as previously described in Example 8, but at a reactortemperature of 400° C. for 70 hours.

The 1-butene yield (wt. %) as a function of time-on-stream (TOS) forreactors comprising the catalyst of Example 1 (520), the catalyst ofExample 2 (530), the catalyst of Example 3 (540), the catalyst ofExample 4 (550), the catalyst of Example 5 (560), and the catalyst ofComparative Example 6 (510) are depicted in FIG. 5. As shown by FIG. 5,the increase in reactor temperature from 300° C. to 400° C. resulted inan overall increase of 1-butene yield and catalyst thermal stability.However, while the isomerization catalytic activity of neither thecatalyst of Comparative Example 6 nor the catalyst of Example 1 appearedto decrease over time, neither catalyst was capable of producing1-butene yields similar to those produced initially at 300° C.Additionally, the catalysts that were produced by surfactant-assistedhydrothermal synthesis (the catalysts of Examples 2-5) each appeared tohave greater 1-butene yields and thermal stability at 400° C. Inparticular, the catalysts of Examples 3 and 5 again maintained animproved 1-butene yield when compared to the other catalysts. This mayfurther indicate that adjusting the pH of the catalyst precursorsolution to be weakly acidic (pH 5) or strongly basic (pH 11) mayimprove the yield and thermal stability of the resulting isomerizationcatalyst.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the disclosure. Since modifications, combinations,sub-combinations and variations of the disclosed embodimentsincorporating the spirit and substance of the disclosure may occur topersons skilled in the art, the scope of the disclosure should beconstrued to include everything within the scope of the appended claimstheir equivalents.

In a first aspect of the present disclosure, a method of producing anisomerization catalyst may comprise preparing a catalyst precursorsolution comprising at least a magnesium precursor, a hydrolyzing agent,and cetrimonium bromide; hydrothermally treating the catalyst precursorsolution to produce a magnesium oxide precipitant; and calcining themagnesium oxide precipitant to produce the isomerization catalyst.

A second aspect of the present disclosure may comprise the first aspectwhere the molar ratio of the magnesium precursor to the hydrolyzingagent in the catalyst precursor solution is from 1:10 to 1:1.

A third aspect of the present disclosure may comprise either of thefirst or second aspects where the molar ratio of the magnesium precursorto polyethylene glycol in the catalyst precursor solution is from 1:0.01to 1:0.1.

A fourth aspect of the present disclosure may comprise any of the firstthrough third aspects further comprising adjusting the pH of thecatalyst precursor solution.

A fifth aspect of the present disclosure may comprise the fourth aspectwhere the pH of the catalyst precursor solution is adjusted to a pH offrom 3 to 7.

A sixth aspect of the present disclosure may comprise the fourth aspectwhere the pH of the catalyst precursor solution is adjusted to a pH offrom 8 to 12.

A seventh aspect of the present disclosure may comprise any of the firstthrough sixth aspects where hydrothermally treating the catalystprecursor solution comprises heating the catalyst precursor solution toa temperature of from 100° C. to 140° C. for a duration of from 48 hoursto 96 hours.

An eighth aspect of the present disclosure may comprise any of the firstthrough seventh aspects where calcining the catalyst precipitantcomprises heating the catalyst precipitant to a temperature of from 450°C. to 650° C. for a duration of from 1 hour to 10 hours.

A ninth aspect of the present disclosure may comprise as isomerizationcatalyst made by the method of any of the first through eighth aspects.

A tenth aspect of the present disclosure may comprise the ninth aspectwhere the surface area of the isomerization catalyst is from 100 m²/g to300 m²/g.

An eleventh aspect of the present disclosure may comprise either of theninth or tenth aspects where the average particle size of theisomerization catalyst is from 10 nm to 50 nm.

In a twelfth aspect of the present disclosure, a method of producing1-butene from a 2-butene-containing feedstock may comprise contactingthe 2-butene-containing feedstock with an isomerization catalyst toproduce an isomerization reaction effluent comprising 1-butene, theisomerization catalyst prepared by a method comprising: preparing acatalyst precursor solution comprising at least a magnesium precursor, ahydrolyzing agent, and cetrimonium bromide; hydrothermally treating thecatalyst precursor solution to produce a magnesium oxide precipitant;and calcining the magnesium oxide precipitant to produce theisomerization catalyst.

A thirteenth aspect of the present disclosure may comprise the twelfthaspect where the isomerization catalyst is disposed in an isomerizationreaction zone.

A fourteenth aspect of the present disclosure may comprise either of thetwelfth or thirteenth aspects where contacting the 2-butene-containingfeedstock with the isomerization catalyst causes the isomerization of atleast a portion of 2-butene in the 2-butene-containing feedstock.

A fifteenth aspect of the present disclosure may comprise any of thetwelfth through fourteenth aspects where the molar ratio of themagnesium precursor to the hydrolyzing agent in the catalyst precursorsolution is from 1:10 to 1:1.

A sixteenth aspect of the present disclosure may comprise any of thetwelfth through fifteenth aspects where the molar ratio of the magnesiumprecursor to polyethylene glycol in the catalyst precursor solution isfrom 1:0.01 to 1:0.1.

A seventeenth aspect of the present disclosure may comprise any of thetwelfth through sixteenth aspects further comprising adjusting the pH ofthe catalyst precursor solution.

An eighteenth aspect of the present disclosure may comprise theseventeenth aspect where the pH of the catalyst precursor solution isadjusted to a pH of from 3 to 7.

A nineteenth aspect of the present disclosure may comprise theseventeenth aspect where the pH of the catalyst precursor solution isadjusted to a pH of from 8 to 12.

A twentieth aspect of the present disclosure may comprise any of thetwelfth through nineteenth aspects where hydrothermally treating thecatalyst precursor solution comprises heating the catalyst precursorsolution to a temperature of from 100° C. to 140° C. for a duration offrom 48 hours to 96 hours.

A twenty-first aspect of the present disclosure may comprise any of thetwelfth through twentieth aspects where calcining the catalystprecipitant comprises heating the catalyst precipitant to a temperatureof from 450° C. to 650° C. for a duration of from 1 hour to 10 hours.

A twenty-second aspect of the present disclosure may comprise any of thetwelfth through twenty-first aspects where the surface area of theisomerization catalyst is from 100 m²/g to 300 m²/g.

A twenty-third aspect of the present disclosure may comprise any of thetwelfth through twenty-second aspects where the average particle size ofthe isomerization catalyst is from 10 nm to 50 nm.

It should now be understood that various aspects of the presentdisclosure are described and such aspects may be utilized in conjunctionwith various other aspects.

It is noted that one or more of the following claims utilize the term“where” as a transitional phrase. For the purposes of defining thepresent disclosure, it is noted that this term is introduced in theclaims as an open-ended transitional phrase that is used to introduce arecitation of a series of characteristics of the structure and should beinterpreted in like manner as the more commonly used open-ended preambleterm “comprising.”

It should be understood that any two quantitative values assigned to aproperty may constitute a range of that property, and all combinationsof ranges formed from all stated quantitative values of a given propertyare contemplated in this disclosure. It should be appreciated thatcompositional ranges of a chemical constituent in a stream or in areactor should be appreciated as containing, in some embodiments, amixture of isomers of that constituent. For example, a compositionalrange specifying butene may include a mixture of various isomers ofbutene. It should be appreciated that the examples supply compositionalranges for various streams, and that the total amount of isomers of aparticular chemical composition can constitute a range.

Having described the subject matter of the present disclosure in detailand by reference to specific embodiments, it is noted that the variousdetails described in this disclosure should not be taken to imply thatthese details relate to elements that are essential components of thevarious embodiments described in this disclosure, even in cases where aparticular element is illustrated in each of the drawings that accompanythe present description. Rather, the appended claims should be taken asthe sole representation of the breadth of the present disclosure and thecorresponding scope of the various embodiments described in thisdisclosure. Further, it will be apparent that modifications andvariations are possible without departing from the scope of the appendedclaims.

What is claimed is:
 1. A method of producing an isomerization catalyst,the method comprising: preparing a catalyst precursor solutioncomprising at least a magnesium precursor, a hydrolyzing agent, andcetrimonium bromide; hydrothermally treating the catalyst precursorsolution to produce a magnesium oxide precipitant; and calcining themagnesium oxide precipitant to produce the isomerization catalyst. 2.The method of claim 1, where the molar ratio of the magnesium precursorto the hydrolyzing agent in the catalyst precursor solution is from 1:10to 1:1.
 3. The method of claim 1, where the molar ratio of the magnesiumprecursor to cetrimonium bromide in the catalyst precursor solution isfrom 1:0.01 to 1:0.1.
 4. The method of claim 1, further comprisingadjusting the pH of the catalyst precursor solution.
 5. The method ofclaim 4, where the pH of the catalyst precursor solution is adjusted toa pH of from 3 to
 7. 6. The method of claim 4, where the pH of thecatalyst precursor solution is adjusted to a pH of from 8 to
 12. 7. Themethod of claim 1, where hydrothermally treating the catalyst precursorsolution comprises heating the catalyst precursor solution to atemperature of from 100° C. to 140° C. for a duration of from 48 hoursto 96 hours.
 8. An isomerization catalyst produced by the method ofclaim
 1. 9. The isomerization catalyst of claim 8, where the surfacearea of the isomerization catalyst is from 100 m²/g to 300 m²/g.
 10. Theisomerization catalyst of claim 8, where the average particle size ofthe isomerization catalyst is from 10 nm to 50 nm.
 11. A method ofproducing 1-butene from a 2-butene-containing feedstock, the methodcomprising: contacting the 2-butene-containing feedstock with anisomerization catalyst to produce an isomerization reaction effluentcomprising 1-butene, the isomerization catalyst prepared by a methodcomprising: preparing a catalyst precursor solution comprising at leasta magnesium precursor, a hydrolyzing agent, and cetrimonium bromide;hydrothermally treating the catalyst precursor solution to produce amagnesium oxide precipitant; and calcining the magnesium oxideprecipitant to produce the isomerization catalyst.
 12. The method ofclaim 11, where contacting the 2-butene-containing feedstock with theisomerization catalyst causes the isomerization of at least a portion of2-butene in the 2-butene-containing feedstock.
 13. The method of claim11, where the molar ratio of the magnesium precursor to the hydrolyzingagent in the catalyst precursor solution is from 1:10 to 1:1.
 14. Themethod of claim 11, where the molar ratio of the magnesium precursor tocetrimonium bromide in the catalyst precursor solution is from 1:0.01 to1:0.1.
 15. The method of claim 11, further comprising adjusting the pHof the catalyst precursor solution.
 16. The method of claim 15, wherethe pH of the catalyst precursor solution is adjusted to a pH of from 3to
 7. 17. The method of claim 15, where the pH of the catalyst precursorsolution is adjusted to a pH of from 8 to
 12. 18. The method of claim11, where hydrothermally treating the catalyst precursor solutioncomprises heating the catalyst precursor solution to a temperature offrom 100° C. to 140° C. for a duration of from 48 hours to 96 hours. 19.The method of claim 11, where calcining the catalyst precipitantcomprises heating the catalyst precipitant to a temperature of from 450°C. to 650° C. for a duration of from 1 hour to 10 hours.
 20. The methodof claim 11, where the surface area of the isomerization catalyst isfrom 100 m²/g to 300 m²/g.